The present invention relates to a stencil of the type including a support forming a design or pattern that is to be transferred onto a surface to be printed, with a non-planar profile and, in particular, a convex profile. The stencil according to the invention is most particularly suited to producing designs or patterns printed on hair or other certain parts of the body.
Stencils have been widely used for producing designs or patterns printed on flat surfaces. Typically, a stencil of this kind is made of a relatively rigid support from which is cut the pattern that is to be produced. The support is applied to the element that is to be decorated, and a colorant is applied so as to deposit the colorant onto the surface that is to be printed and do so in the pattern defined by the design made in the support. The colorant may be applied using a brush or an applicator, particularly of the cellular foam type, pierced at its center with a duct communicating with a container on which the foam is mounted. This technique is used particularly for interior decorating or in the field of cosmetics for applying body make-up. It works entirely satisfactorily when the surface to be decorated is flat or approximately flat.
Problems arise when this technique is to be used for decorating non-planar surfaces, such as the hair, or certain convex surfaces of the body. This is because the center of the pattern can easily be applied at the desired point using a rigid stencil of the type described hereinabove but, because of the curvature of the head or other body areas, the edges of the pattern are not clearly defined.
Making the stencil from a support made of flexible material does not satisfactorily solve the problem in so far as its use requires the stencil to be held in place on the scalp at the same time as application of the product. Experience has shown that, particularly on account of the difficulty of holding the flexible support in position on the head, it is difficult to apply the product to the hair without calling on a third party for assistance.
Thus, one of the objects of the invention is to produce a stencil suited for decorating or applying make-up to non-planar surfaces, and this stencil at least partially solves the aforementioned problems.
In particular, one object of the invention is to produce a stencil, suited in particular to applying make-up to the hair or applying body make-up, that someone can use without requiring the help of a third party.
Another object of the invention is to produce a stencil which is simple to use and economical to produce.
It should be understood that the invention could still be practiced without performing one or more of the preferred objects and/or advantages set forth above. Still other objects will become apparent after reading the following description of the invention.
To achieve these and other advantages, and in accordance with the purposes of the invention, as embodied and broadly described herein, the invention includes a stencil. The stencil comprises a substantially flexible sheet bearing a pattern that is to be reproduced on a convex surface. One region of the sheet, located near a peripheral edge, is attached to a substantially rigid frame, the flexible sheet being mounted on the frame in such a way as to form a dome inside the frame. Preferably, the frame has a substantially annular shape, but the invention in its broadest aspects could be practiced with many differently shaped frames.
Preferably, the substantially rigid frame allows the stencil to be positioned at the desired point, particularly on the head, and held in place there with ease. The flexible sheet bearing the design that is to be reproduced can be permanently shaped to the curvature of the surface that is to be decorated. The action is simple, and application may be performed without having to involve a third party. By way of indication, the stencil may have a diameter that may be of the order of 10 cm to 15 cm. The rigidity of the frame is at least such that this frame remains in shape in the absence of appreciable stress and, in particular, does not deform under its own weight. The radius of curvature formed by the dome of the flexible sheet is of the same order as the radius of curvature of the surface that is to be decorated, so that the entire design can rest against the surface that is to be treated.
The flexible sheet is preferably not elastically deformable (in the case of a multi-layer sheet, at least one of the layers is made of a material which is not elastically deformable) so that the pattern, produced by removing material, does not deform during application.
As a preference, the peripheral region by which the flexible sheet is attached to the frame has an inner edge and an outer edge, the inner edge having a radius R smaller than the radius R+xcex5 which that portion of the flexible sheet that extends inside the inner edge would form if the flexible sheet were not secured to the frame.
Advantageously, 1.01 * Rxe2x89xa6R+xcex5xe2x89xa61.05 * R. More preferably, 1.01 * Rxe2x89xa6R+xcex5xe2x89xa61.02 * R.
Such differences in radii are particularly advantageous in that they can be achieved entirely naturally by a phenomenon known as xe2x80x9cpost-shrinkagexe2x80x9d which is observed when molding materials such as thermoplastics. In general, xe2x80x9cpost-shrinkagexe2x80x9d in the sphere of molding is seen as a constraint that has to be accounted for in the molding process when determining the operating parameters thereof.
Advantageously, the frame is formed of at least two parts which can be folded one onto the other. Thus, a structure is produced that makes it possible to obtain a relatively large-sized pattern for printing (particularly from 10 to 15 cm), but which can be folded so as to occupy less space in the storage position. For this purpose, the parts of the annular frame may be connected together by an articulation, particularly of the film hinge type.
According to a preferred embodiment of the invention, the rigid frame is obtained by molding a first thermoplastic in a mold, in one plane of which is held the flexible sheet, already formed and cut to the desired size and shape, the sheet having at least one layer of a second thermoplastic which is physico-chemically compatible with the first thermoplastic, so as to allow the frame to attach to the flexible sheet along the peripheral attachment region. Physico-chemically compatible materials are materials which, in the molten or softened state, are able to weld together.
This characteristic of the stencil according to the invention is quite particularly advantageous in that it makes it possible to obtain a uniform dome, making it possible to obtain a printing pattern with a very sharp outline. Specifically, the advantageous effect of such a characteristic stems from the xe2x80x9cpost-shrinkagexe2x80x9d phenomenon described previously, which is observed in the molding processes, particularly the molding of thermoplastics.
In practice, there are several advantageous aspects associated with producing the stencil by molding, using a technique similar to the so-called In-Mold Labeling (IML) technique, known in the field of labeling certain objects which are made of thermoplastic, particularly bottles.
On the one hand, it allows the peripheral edge of the sheet to be attached to the rigid frame in a perfectly uniform way with no creases or other irregularities. This is because attachment (which occurs by localized xe2x80x9cfusionxe2x80x9d of mutually compatible materials) of the peripheral edge of the flexible sheet to the annular frame occurs almost instantaneously when the first molten thermoplastic is injected under pressure, this fusing being with a sheet held flat in the mold. As a preference, the attachment region extends continuously over 360xc2x0.
On the other hand, because of the xe2x80x9cpost-shrinkagexe2x80x9d of the material of which the frame is made, the sheet, the peripheral edge of which was secured to the rigid frame beforehand, is forced, under the effect of centripetal forces applied uniformly over 360xc2x0, to deform into the shape of a homogeneous dome, able in particular to approximately follow the curvature of the head. These centripetal forces, exerted uniformly over 360xc2x0, effectively result in a slight reduction in the diameter of the frame, which reduction causes the sheet to permanently adopt the dome shape. In practice, the peripheral edge of the flexible sheet attaches to the frame in the mold almost instantaneously, especially in a cooled mold, whereas the xe2x80x9cpost-shrinkagexe2x80x9d phenomenon takes place over a time which may be as long as 48 hours, and, therefore, well after the sheet has been irremovably attached to the frame. This xe2x80x9cpost-shrinkagexe2x80x9d phenomenon obviously occurs in all directions in space, but is most noticeable over the largest diameter of the molded object, namely the circumference. In the case of an annular frame with a diameter of 100 mm to 150 mm, the reduction in diameter may, depending on the material used and the molding conditions, be of the order of 1 mm to 7.5 mm.
Advantageously, the first thermoplastic is a polyolefin chosen, for example, from polyethylenes, polypropylenes, polyacetates and polycarbonates.
Advantageously also, the flexible sheet includes at least two layers including a first layer made with the second thermoplastic, and a second layer capable of forming a decorative layer and made of a material such as paper or polyethylene terephthalate. The xe2x80x9cpost-shrinkagexe2x80x9d phenomenon does not occur on the flexible sheet provided it is kept at a temperature below the softening or melting temperature of the thermoplastic of which it is made, except in the highly localized region of its periphery where it is xe2x80x9cweldedxe2x80x9d to the frame. Thus, no appreciable reduction in the diameter of the sheet occurs, so the sheet has no other choice but to shape itself into the desired dome shape.
The stencil according to the invention is advantageously used for applying a cosmetic product to apart of the body. For example, the stencil could be used to apply hair coloring to hair.
In another aspect of the invention, there is provided a method for manufacturing a stencil comprising a substantially flexible sheet bearing a pattern that is to be reproduced on a convex surface, and of which one region, located near a peripheral edge, is attached to a substantially rigid frame in the form of an annular element, for example, the method comprising producing the frame, by molding a first thermoplastic in a mold, in one plane of which is held the flexible sheet, already formed and cut to the desired size and shape, the sheet having at least one layer of a second thermoplastic which is physico-chemically compatible with the first thermoplastic, so as to allow the frame to attach to the flexible sheet along the peripheral attachment region, a reduction in the diameter of the frame thus attached to the flexible sheet, under the effect of the xe2x80x9cpost-shrinkagexe2x80x9d of the first thermoplastic, causing the flexible sheet to form a dome inside the frame. The first and second thermoplastics may be identical or different, the only condition being that they be mutually compatible.
More specifically, the method may include placing the flexible sheet, already formed and cut to the desired size and shape, in a mold, the mold being kept at a temperature below the softening temperature of the second thermoplastic, injecting the first thermoplastic under pressure into an annular region of the mold so as to form the frame, the annular region being arranged in such a way that, as the frame is molded, the flexible sheet becomes welded to the frame along the peripheral attachment region, and demolding the stencil.
The mold is preferably of the type with two separable parts. The flexible sheet may be held in position in the mold by suction. The mold may be kept at a temperature close to about 45xc2x0 C., it being possible for the first thermoplastic to be injected into the annular region of the mold at a temperature of from about 180xc2x0 C. to about 240xc2x0 C.
According to one aspect of the invention, a stencil is provided. The stencil comprises a substantially rigid frame, and a substantially flexible sheet having at least one aperture passing through the sheet and defining a pattern, a peripheral region of the sheet being attached to the frame, the flexible sheet forming a dome within the frame configured to allow the pattern of the at least one aperture to be reproduced on a substantially convex surface.
According to another aspect of the invention, a method of applying make-up to the hair or body is provided. The method comprises placing a stencil comprising a substantially rigid frame, and a substantially flexible sheet having at least one aperture passing through the sheet and defining a pattern, a peripheral region of the sheet being attached to the frame, the flexible sheet forming a dome within the frame configured to allow the pattern of the at least one aperture to be reproduced on a substantially convex surface on an area of the body, and applying a cosmetic product to the area of the body by passing the cosmetic product through the at least one aperture in the sheet.
According to a further aspect of the invention, a method of manufacturing a stencil having a substantially rigid frame and a substantially flexible sheet having at least one aperture passing through the sheet and defining a pattern, a peripheral region of the sheet being attached to the frame is provided. The method comprises providing a flexible sheet in a mold, passing a first thermoplastic into the mold to mold a substantially rigid frame, permitting the first thermoplastic of the frame to become attached to a peripheral region of the sheet including a second thermoplastic which is physico-chemically compatible with the first thermoplastic, and reducing at least one dimension of the frame to form the flexible sheet into a dome shape within the frame.
According to yet another aspect of the invention, a stencil for applying make-up to the hair and body is provided. The stencil comprises a substantially annular frame, and a flexible concave surface within the frame, the concave surface having a pattern thereon.
Beside the structural arrangements set forth above, the invention could include a number of other arrangements, such as those explained hereinafter. It is to be understood that both the foregoing description and the following description are exemplary, and are intended to provide further explanation of the invention as claimed.